California ADU rules · Alameda County
Can I Build an ADU in Berkeley?
Yes — you can build an ADU in Berkeley. California's statewide ADU law requires every city, including Berkeley, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local ruleOutside Hillside Overlay: 1 ADU + 1 JADU. Inside Hillside Overlay: 1 ADU OR 1 JADU (not both).
Berkeley's Hillside Overlay District ('-H', the Berkeley hills) allows only one ADU or one JADU on a single-family lot, rather than the one-ADU-plus-one-JADU that applies elsewhere in the city.
Units on a multifamily lot
CA state lawConversion ADUs (≥1, up to 25% of units) + up to 8 detached
Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,200 sq ft
Outside the Hillside Overlay, Berkeley follows the state default (up to 1,200 sq ft; 1,000 sq ft for a 2+-bedroom unit). INSIDE the Hillside Overlay, a new-construction detached or attached ADU is capped at 800 sq ft — the state-protected floor, applied as the local maximum in the hills.
Max attached ADU size
CA state law50% of the primary dwelling, but ≥850 sq ft (≥1,000 sq ft for 2+ bedrooms) is always allowed
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule20 ft
Outside the Hillside Overlay, Berkeley allows ADUs up to 20 ft — MORE generous than the 16-ft state base. INSIDE the Hillside Overlay District ('-H'), the maximum is 16 ft. Conversions of existing legal structures may keep their existing height; attached ADUs are capped at 25 ft or the underlying zone limit.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
CA state lawUp to 1 space
At most 1 space per ADU (or per bedroom, whichever is less) — and waived in the common cases below.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Berkeley-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Hillside Overlay District ("-H")
In Berkeley's Hillside Overlay (the Berkeley hills, mapped with the '-H' suffix), an ADU is more constrained than elsewhere: only one ADU OR one JADU per single-family lot, a 16-ft height limit (vs. 20 ft citywide), and an 800 sq ft cap on new-construction ADUs. Decks/balconies on ADU roofs are not allowed.
Very High Fire Hazard Severity Zone (hillside)
Much of the Hillside Overlay sits in a Very High Fire Hazard Severity Zone; ADUs remain allowed but must meet additional fire-safety and building-code standards (defensible space, ignition-resistant construction) that can constrain a detached unit.
Landmarks & historic districts
An ADU on a designated City landmark or in a historic district may trigger additional historic-preservation review beyond the ministerial ADU path.
Berkeley has its own ADU ordinance in Berkeley Mun. Code Ch. 23.306 (with Ch. 12.99), reviewed and approved by a ministerial Zoning Certificate within the state 60-day window. The defining local wrinkle is the Hillside Overlay District ('-H', the Berkeley hills): there, a single-family lot gets only one ADU OR one JADU (not both), ADUs are capped at 16 ft and 800 sq ft, and roof decks are barred — markedly tighter than the rest of the city, where Berkeley actually allows a more generous 20-ft height. Most of the Hillside Overlay also lies in a Very High Fire Hazard Severity Zone, adding fire-safety construction standards. Confirm a parcel's overlay and fire-zone status with Berkeley Planning before relying on any single number.
Frequently asked questions
Can I build an ADU in Berkeley?
Yes. California's statewide ADU law requires Berkeley to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Berkeley?
A detached ADU of at least 1,200 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Berkeley?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Berkeley?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Berkeley?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Berkeley?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Berkeley Mun. Code Ch. 23.306 (with Ch. 12.99)
- Berkeley Mun. Code § 23.306.020
- Berkeley Mun. Code § 23.306.030 (Table 23.306-2)
- Berkeley Mun. Code § 23.306.030 / Table 23.306-2
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-28. This is an AI-assisted summary of Berkeley's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Berkeley Planning before relying on it.
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